In the past, it was common practice for ophthalmologists to arrange different instruments and examination chairs or stools at different locations in an office or operatory. This practice required that both the doctor and patient move from location to location which interrupted the examination and caused needless delays.
In an effort to shorten the examination time and increase efficiency, instrument support equipment has been designed to enable both the patient and doctor to remain in the same location while the instrumentation is moved into position as needed. This has been accomplished in the prior art by mounting a number of different instruments on a post carried by a base, e.g., U.S. Pat. Nos. 1,494,666 to Clement and 2,149,141 to Hunsicker, and/or mounting the instruments to a movable arm assembly which is positionable between the doctor and patient, e.g., U.S. Pat. Nos. 3,201,795 to Cuppers et al and 3,572,913 to Korh et al.
More recent designs of supports for ophthalmic examination instruments include a cabinet base which supports a post carrying a number of instruments, and a separate horizontal table mounted to the cabinet which is positionable over the lap of the patient seated upon a chair. The horizontal table mounts a number of instruments and is extensible relative to the supporting cabinet and the patient to position the desired instrument near the patient as required during the examination. See, for example, U.S. Pat. Nos. 4,421,394 to Schon et al and 4,643,547 to Collins et al.
In the ophthalmic instrument supports of the type described in the patents to Schon et al and Collins et al, for example, the ophthalmological chairs which support the patient can be raised and lowered to align the patient with the instruments on the horizontal table portion of the support. No provision is made in such supports, however, to readily adjust the lateral position of the chair and patient with respect to the horizontal table. Depending upon the size of the patient, it may be necessary to move the chair laterally toward or away from the horizontal table in order to properly align the patient with the ophthalmic instrumentation.
Lateral movement of ophthalmological chairs has been obtained in the prior art by mounting the chair to an adjustable base support. Such base supports include a top plate which mounts the chair, and a bottom plate upon which the top plate is laterally movable. Although capable of adjusting the position of an ophthalmological chair, such prior art base supports have not been designed to mount relatively heavy chairs and are not effective to securely lock the top plate relative to the bottom plate once the position of the chair has been adjusted.